1. Field of the Invention
The subject invention generally pertains to fans and more specifically to a heated fan housing.
2. Description of Related Art
Residential and commercial air handling units, such as furnaces, air conditioners, heat pumps, etc., often include a blower or fan that forces air across a heater. Ductwork then conveys the heated air to where it is needed. The heater may be the air handling unit's primary or supplemental source of heat. Often, the heater is simply an electrical resistance heating coil installed at the blower's suction or discharge opening. There are, however, other types of heaters and mounting locations.
A heater can be installed inside the blower housing, outside the blower housing, or at the blower's suction or discharge opening. A heater mounted inside a blower housing is disclosed in U.S. Pat. No. 1,421,221. Although such a design may provide effective heat transfer, the heater appears to disturb or obstruct the airflow significantly.
Heaters mounted outside the blower housing are disclosed in U.S. Pat. Nos. 4,526,510; 2,368,392 and 2,053,036. In each of these cases, the wall of the blower housing creates a detrimental heat shield between the heat source and the air to be heated. Even if the wall of the blower housing were made of a highly thermally conductive material, the blower wall would still provide some thermal resistance. Moreover, a heater mounted outside the blower housing adds additional volume to an air handling unit.
A heater installed at a blower housing's discharge opening is disclosed in U.S. Pat. No. 2,856,162. A heater at such a location impedes the airflow because the heater lies directly across the path of the air.
U.S. Pat. No. 4,313,493 shows a heater that has one portion installed outside the blower housing and another portion extending across the blower's discharge opening. With such an arrangement, the blower wall creates a heat shield between the air and the portion of the heater that is outside the blower housing, and the rest of the heater obstructs the airflow at the blower's discharge opening.